It has been known for many years to install primary windows on a dwelling and then add secondary or storm windows. This process requires two installations even where the secondary windows are installed immediately.
There continues to be a need to improve installation efficiency in new construction and in after market upgrades. Preferably such improvements would be achievable without a substantial increase in cost or complexity of the windows. Preferably such improvements would be commercially viable in both new construction and in after market improvements.
In addition, where known storm windows are installed on vinyl windows, they reduce the view area or daylight opening of the window. It would be preferable if this undesirable result could be eliminated.
In other potential installations, it is desirable to conserve the appearance of an existing window, which might be for example an antique. In such installations, the existing exterior casings are often badly deteriorated and in need of replacement. There continues to be a need in such installations to be able to incorporate secondary windows on the exterior side of the existing window to both conserve the appearance of the existing window and to protect same from the elements. Preferably, the secondary window could be installed as an upgrade to the existing window without having to remove the existing window.